An electric power steering device provides a supplemental torque based on an inputted steering torque, for the purpose of reducing a driver's steering load. A torque sensor is used to detect the steering torque. For example, in a patent document 1 (i.e., Japanese Patent Laid-Open No. 2003-149062), a variation in torque detection is reduced by providing plural magnetic sensors.
If a problem occurs with the torque sensor, it is desirable to troubleshoot the torque sensor so that an unintended output of the supplemental torque from the electric power steering device that is not intended by the driver is prevented. For example, by configuring the torque sensor to output and compare two output values, the problem with the torque sensor may be detected in some cases. However, when having two output values, determining which one of two values is the correct value may be difficult. Further, when having three or more output values, a majority determination may be performed for determining which one of the three output values is a troubled output. However, such a troubleshooting means increases the number of parts in the device.